/Engine/Source/Runtime/Core/Public/GenericPlatform/GenericPlatformProcess.h
Attempt to launch the provided file name in its default external application. Similar to FPlatformProcess::LaunchURL, with the exception that if a default application isn't found for the file, the user will be prompted with an "Open With..." dialog.
true if the file is launched successfully, false otherwise.
static bool LaunchFileInDefaultExternalApplication ( const TCHAR * FileName, const TCHAR * Parms, [ELaunchVerb::Type](API\Runtime\Core\GenericPlatform\ELaunchVerb__Type) Verb, bool bPromptToOpenOnFailure )